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this is formula based sum...use compound interest formula only add interval to this formula for compoundinginterval is generally 1 as annually compounded....but here it is compounded 4 months in year that is 3 times a year hence interval (i) = 3no of years = 1

When I looked at the question I forgot the CI formula but you can approximate the answer pretty accurately.The first 4 month cycle gives you$2400 x 8/100 x 1/3 = $64

So you know immediately that 3 x 64 is the minimum which is $192.The additional compound interest on top of $64 for each cycle is going to be pretty small (around $64 x 8/100 x 1/3)Looking at the answer choices only C fits.

Hey guys, I'm having a hard time coming up with a quicker way to figure out the Compound Interest problems within the 2 minutes mark.

For this particular question, yes you can use the simple interest version three times and you can get an answer fairly quickly, but when questions become much more complex, i doubt i'm going to be able to work out a quarterly interest for double digit years, all within 2 mins.

Heres the situation via the CI formula way and help me where I'm muddling or complicated it too much:

CI Formula states:2400(1+ \frac{.08}{3})^3^(^1^)

Then, according to PEMDAS, you do the inside parenthesis first. So:Step 1:\frac{.08}{3}= .02666666666 OR .0267S2: 1+.0267=1.0267S3: 1.0267^3 ? Am I seriously expected to do a 5 digit multiplication 4 times? And still finish within the 2 mins?regardless here we go:1.027x1.027718920540+10270001.054729x1.027738310321054580+10547290001.083166683after that, it's pretty simple, but come on, theres got to be an easier way of doing this. the multiplication while easy, is super prone to mistakes, and thus takes in itself, 3ish mins. i say again, there's got to be an easier way.

fractions? still the same thing:

1+\frac{8}{300}\frac{308}{300}^3

here we go again:308x3082464+110400112864x308902892+3385920034762092

then the denominator is easy= 27000000

so now i have to quickly reduce \frac{34762092}{27000000} ?Come on you've got to be kidding me. just finding the reduction itself, will again, be very prone to mistakes, and could easily take over 3 mins.

can any of you guys help me out with figuring out where I'm going wrong here? is there a shortcut i'm not aware of? is there an estimating method that I dont' know?